Referencing arrangement



Dec- 23, 1969 D. F. FRICK. 3,486,045

REFERENCING ARRANGEMENT Filed Feb. 1. 196

INTEGRATED CIRCUIT INTEGRATED CIRCUIT L l- 7 I l 1 l -4 PS L.

l PS i I 1 IE'IlE- E INVENTQR. DAVID E FRICK 7 AT TORNE United States Patent O 3,486,045 REFERENCING ARRANGEMENT David F. Frick, Castro Valley, Califi, assignor to The Singer Company, a corporation of Delaware Filed Feb. 1, 1967, Ser. No. 613,300 Int. Cl. H031: 1/02 US. Cl. 307-296 Claims ABSTRACT OF THE DISCLOSURE A conducting diode establishes an electrical reference between separate power supplies which provide power to interconnected circuits such that the current loops associated with one power supply are independent of the current loops of the other supply so that disturbances, tram sients, etc., in one current loop have no elfect on the other independent current loops.

BACKGROUND OF THE INVENTION This invention relates to referencing means for interconnected circuits having separate power supplies such that the current provided by one power source is electrically independent of the current provided by the other current source, or sources.

Microelectronic circuits have been increasingly utilized by the electronics industry due to their cost, reliability and size. Such circuits generally require relatively low current levels for their operation. Accordingly, when relatively high current output devices, such as typewriter type bars activated by solenoids and the like, are driven, or controlled, by microelectronic circuits, a relatively high current switching device, such as a discrete transistor, is utilized between the microelectronic circuits and the output devices to supply the necessary output current levels. Heretofore in the prior art, activation of the high current output devices has produced relatively high current disturbances, transients, etc., which feedback into the microelectronic circuits causing malfunctions, destruction of the microelectronic circuits and other undesirable results.

Accordingly, one object of this invention is to enable relatively low current devices, such as microcircuits, to drive relatively high current output devices without high current destructive disturbances, transients, and the like, being induced into the low current devices.

Another object of this invention is to provide an electrical reference between at least two power sources such that the current loops associated with one power source are electrically independent of at least one current loop of the other power source.

Still another object of this invention is to provide an electrical reference between a relatively low current source and a relatively high current source such that the current loops of the low current source are electrically independent of the high current source current loops even though the circuitry associated with the current sources are electrically coupled together.

SUMMARY OF THE INVENTION Briefly described, these and other objects of the present invention are accomplished by electrical referencing apparatus which includes a relatively low current power source having at least two voltage terminals, and a relatively high current power source also having at least two voltage terminals. A relatively low current device, such as an integrated circuit, is coupled to the low current source. A relatively high current output device, including current switching means, is coupled to the high current supply with the current switching means being controlled by a signal developed by the integrated circuit. An electrical Patented Dec. 23, 1969 See BRIEF DESCRIPTION OF THE DRAWINGS This invention, as well as other objects, features and advantages thereof, will be readily apparent from consideration of the following detailed description relating to the annexed drawings in which:

FIG. 1 is a schematic diagram illustration of one embodiment of the present invention; and

FIG. 2 illustrates a modification of the embodiment of the present invention shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIG. 1 illustrates one embodiment of the present invention as including a relatively low current device 11, such as integrated circuitry, which produces an output signal, on the lead 12, that is applied to and controls a relatively high current switching device, such as a PNP transistor 30. The integrated circuitry 11 may take any desired form in accordance with the present invention, it only being necessary that the circuitry 11 produce at least one output signal and have as a final stage a semiconductor device, such as an NPN transistor 20, of opposite conductivity type to the transistor 30 which is electrically coupled to the transistor 20. As shown by FIG. 1, the NPN transistor 20 has its emitter 21 coupled to ground potential, its base 22 coupled to control circuits (not shown) and its collector 23 coupled to a positive potential by way of a load resistor 13. The output lead 12 is coupled to the junction of the resistor 13 with the collector 23. As will be apparent to those skilled in the art, the transistor 20 and its associated components comprise a grounded emitter transistor amplifier.

Power for the relatively low current, integrated circuit device 11 is provided by a regulated, relatively low current, power supply 14. The negative potential of the power source 14 is grounded by way of the lead 15 while the positive potential is coupled to the collector 23 of the transistor 20 by way of the resistor 13 and the lead 16.

In accordance with the present invention, an output signal produced by the low current device 11, and appearing on the lead 12, is used to control current to, or through, a relatively high current device. For purposes of explanation, FIG. 1 illustrates a typical relatively high current output device to be a solenoid coil 34 'which may be utilized to operate selected typewriter type bars, tape punches, relays clutches or the like. A suitable current switching device, such as a PNP transistor 30, is serially connected between the solenoid 34 and an unregulated power source 36 of relatively high operating current for the solenoid coil 34. One end of the solenoid coil 34 is coupled to the negative potential of the power source by way of the lead 38, while the other end of the solenoid coil 34 is coupled to the collector 33 of the transistor 30 The emitter 31 of the transistor 30 is coupled to the positive voltage terminal of the power source 36 by way of the lead 37. A diode 35 coupled across the solenoid coil 34 functions as a damping diode in a well-known manner. Unlike the power source 14, none of the voltage levels of the power source 36 are at a reference potential, such as ground.

Conduction of the transistor 30 is controlled by the output of the integrated circuit 11 appearing on the lead 12 which is coupled to the base 32 of the transistor 30 by way of the resistor 40. Further, the base 32 of the transistor 30 is coupled to the positive potential of the power source 14, by way of the current-limiting resistor 41, which positive potential renders the transistor 30 nonconductive in the absence of an output signal from the transistor 20. If desired, the resistor 40 can be replaced with a capacitor (not shown) to provide capacitive coupling between the transistors and 30.

To enable the output of the low current device 11 to control the current switching device 30, an electrical reference need be established between the two power sources 14 and 36. This is accomplished, in accordance with the present invention, in a manner that causes the relatively low current loops associated with the low current source 14 to be independent of the relatively high current loop associated with the high current source 36 by means of a serially connected network consisting of a diode 43 and a bleeder resistor 42. The series resistor 42, diode 43 network is coupled across the voltage terminals of the power source 14 such that the diode 43 is forwardly biased and with the junction of the resistor 42 with the diode 43 being coupled to the emitter 31 of the transistor 30 by way of the lead 45.

Assume now that the transistor 20 is rendered nonconducting, by other circuitry (not shown) within the integrated circuit device 11 in a well-known manner. This causes the potential on the base 32 of transistor 30 to be substantially equal to the potential at the collector 23 of transistor 20 which, since the transistor 20 is nonconductive, is equal to the positive potential of the power source 14 appearing on lead 16. The power source 14 forwardly biases the diode 43, causing it to be conducting with current flow from the negative potential of the source 14, which appears on lead 15, through the resistor 42, the diode 43 and to the positive side of the source 14. The major portion of the voltage magnitude of the source 14 is dropped across the resistor 42 since, when conducting, the diode 43 presents a relatively low impedance having less than one volt dropped across it. Accordingly, the potential seen at the emitter 31 of the transistor 30 (with respect to the base 32) is the positive potential of the source 14 minus the relatively small drop across the diode 43. The potential at the base 32 of the transistor 30- is, as described above, equal to the positive potential of the source 14, which causes the base 32 to be more positive than the emitter 31 to render the PNP transistor 30 nonconducting. Since the power source 36 has no efiect on the emitter 31 to base 32 potential of the transistor 30, the relative voltage magnitude of the power source 36 with respect to the power source 14 has no effect on the conduction, or nonconduction, of the transistor 30. Also, the relative voltage magnitudes of the power sources 14 and 36 have no effect on the conduction or nonconduction of the diode 43. Further, the coupling resistor 40 can be replaced with a coupling capacitor (not shown) without effecting the nonconduction of the transistor 30 since the full positive potential of the source 14 will appear on the base 32 by way of the resistor 41 when the transistor 20 is nonconducting.

Assume now that the transistor 20 is rendered conductive for a period of time by circuitry (not shown) Within the integrated circuit device 11. During the time transistor 20 is conducting, a current loop exists from the negative potential of power source 14, through the emitter 21 and collector 23 of transistor 20, the resistor 13 and to the positive side of the source 14. Conduction of the transistor 20 causes the potential at the collector 23 to be substantially equal to the potential at the emitter 21, which is ground potential. This causes the base 32 of transistor 30 to be less positive than its emitter 31 which turns on the transistor 30. This causes another current loop associated with the power source 14 to exist between the negative, or grounded side, of the source 14, through the transistor 20, the resistor 40, the base 32, emitter 31 junction of transistor 30, the diode 43 and the positive side of the source 14. In this current loop the emitter-base junction of transistor 30 and the diode 43 constitute two serially connected diodes. Another current loop associated with the source 14 exists between ground potential, through the transistor 20, the resistors 40 and 41 and the positive side of the source 14. Still another current loop exists between ground potential, through the series resistor 42, diode 43 network and the positive side of the source 14.

Conduction of the current switching transistor 30 causes a relatively high current loop to exist from the negative side of the source 36, the lead 38, through the collector 33 and emitter 31 electrodes of the transistor 30, the lead 37 to the positive side of the source 36. This current flow through the coil 34 activates the associated solenoid (not shown), or like output device. Since the power source 36 never electrically sees ground potential, the relatively high current produced by the source 36 remains totally confined to the loop defined by the source 36, the lead 38, the coil 34, the collector 33 to emitter 31 of transistor 30, and the lead 37. When the transistor 20 is again rendered nonconductive, the base 32 of transistor 30 is again positive with respect to the emitter 31 to cause transistor 30 to be nonconductive to eliminate current flow from the source 36. When transistor 30 is caused to be nonconductive, any oscillations, or ringing, that may tend to occur due to the coil 34 are damped out, in a well-known manner, by the diode 35.

As will now be apparent from the above description, the diode 43 is always conducting and the conduction of diode 43 is independent of whether transistors 20 and/ or 30 are conductive or nonconductive. The conduction of diode 43 establishes an electrical reference between the two power sources 14 and 36 such that causing the transistor 20 to be alte'rnately conducting and nonconducting enables efiicient current switching of the transistor 30. However, since the power source 36 never sees ground potential, transients, disturbances, and the like, in the relatively high current provided by the source 36 have no effect on the relatively small currents provided by the source 14 even though, when transistor 20 is conducting current flow through the emitter 31 electrode of transistor 30 is provided by both current sources 14 and 36. In other words, the relatively high current loop associated with the power source 36 is electrically independent of the relatively low current loops associated with the power source 14 to eliminate cross talk, or feedback, between the current loops associated with the power sources 14 and 36, that may tend to damage the low current device 11.

As will be apparent to those skilled in the art, the leakage current of transistor 20 and the emitter-base leakage current of transistor 30 is provided by the source 14; whereas, the emitter-collector leakage current of transistor 30 is supplied by the source 36. Further, the arrangement illustrated in FIG. 1 does not require an additional power source for biasing the transistor 30. Also, FIG. 1 shows only one current switching device 30, one output solenoid 34 and one low current transistor 20. It is to be understood, however, that the low current device 11 may contain a plurality of output stages, such as transistor 20, which may be utilized to operate a plurality of output devices 34. As will also be apparent to those skilled in the art, a capacitor substituted for the resistor 40, as discussed above, will pass a pulse appearing on the collector 23 due to turning transistor 20 on and off in a wellknown manner to control the switching transistor 30.

FIG. 2 illustrates a modification of the device shown in FIG. 1. Since the operation of the circuit of FIG. 2 is substantially identical to that of FIG. 1, it will not be described in detail. However, as shown by FIG. 2, the relatively high current source associated with the solenoid coil and current switching transistor can be grounded rather than the low current source. Also, the complementary transistors of FIG. 1 can be reversed by reversing the polarities of the high and low current sources and reversing the connections of the damping diode and the referencing diode.

It is to be understood, of course, that the foregoing disclosure relates only to specific embodiments of the present invention and that numerous modifications and alterations may be made therein without departing from the spirit and scope of this invention as set forth in the appended claims.

What is claimed is:

1. Electrical referencing means comprising:

a first power source having only two voltage terminals,

one of which is grounded;

a second power source having only two voltage terminals, none of which are grounded;

first circuitry coupled to said first power source and having at least one current loop associated therewith;

second circuitry coupled to said second power source and having at least one current loop associated therewith; and means for establishing an electrical reference between said first and second power sources such that at least one current loop associated with the first power source is electrically independent of at least one current loop associated with the second power source;

said means including a series diode-resistor network coupled across the two voltage terminals of one power source with the junction of said diode with said resistor being coupled to a voltage terminal of the other power source for biasing said second circuitry.

2. The apparatus according to claim 1 wherein:

one said power source is a relatively low current source and the other power source is a relatively high current source.

3. The apparatus according to claim 1 further includmg:

electrical coupling means interconnecting the circuitry associated with one power source to the circuitry associated with the other power source.

4. The apparatus according to claim 3 wherein:

an NPN transistor associated with the circuitry of one power source is coupled to a PNP transistor associated with the circuitry of the other power source by said electrical coupling means.

5. The apparatus according to claim 1 wherein:

said diode in said series diode-resistor network is forwardly biased by the power source across which the series network is coupled.

6. Electrical referencing means comprising:

a relatively low current power source having only two voltage terminals;

a relatively high current power source having only two voltage terminals;

one of the voltage terminals associated with one of said power sources having a reference potential;

an integrated circuit coupled to said relatively low current power source;

current switching means coupled to said relatively high current power source and controlled by said integrated circuit; and

means for establishing an electrical reference between said power sources such that the currents produced by said power sources are electrically independent of one another whereby disturbances and transients associated with said relatively high current source have no elfect on said relatively low current source;

said means including a series resistor-unidirectional current device network coupled across said two voltage terminals of said relatively low current power source such that said unidirectional current device is forwardly biased and with the junction of said resistor with said unidirectional current device being coupled to a voltage terminal of the other power source for biasing said current switching means.

7. The apparatus according to claim 6 further including:

a relatively high current output device coupled to said switching means which is activated in response to the activation of said switching means by said integrated clrcuit.

8. The apparatus according to claim 6 wherein:

said switching means includes a transistor of one conductivity type, and

said integrated circuit includes a transistor of an opposite conductivity type which is coupled to and controls said switching means transistor.

9. The apparatus according to claim 8 wherein:

the junction of said resistor with said unidirectional current device is coupled to the emitter electrode of the switching transistor.

10. The apparatus according to claim 9 wherein:

the opposite conductivity type integrated circuit transistor has its collector electrically coupled to the base of said switching transistor.

References Cited UNITED STATES PATENTS 3,122,646 2/1964 Deysher et al. 307296 XR DONALD D. FORRER, Primary Examiner I. ZAZWORSKY, Assistant Examiner US. 01. X.R. 

